Method of depositing a metal-containing film

ABSTRACT

A method of depositing a Group IV metal-containing film on a substrate by conveying one or more of certain Group IV organometallic compounds in a gaseous phase to a deposition reactor containing a substrate and decomposing the one or more Group IV organometallic compounds to form a film of a Group IV metal on the substrate is provided. Such Group IV metal-containing films are particularly useful in the manufacture of electronic devices.

This application claims the benefit of provisional application Ser. No.60/460,791, filed on Apr. 5, 2003, and provisional application Ser. No.60/513,476, filed on Oct. 22, 2003.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of organometalliccompounds. In particular, the present invention relates to the certainorganometallic compounds suitable for use in vapor deposition processes.

Metal films may be deposited on surfaces, such as non-conductivesurfaces, by a variety of means such as chemical vapor deposition(“CVD”), physical vapor deposition (“PVD”), and other epitaxialtechniques such as liquid phase epitaxy (“LPE”), molecular beam epitaxy(“MBE”), chemical beam epitaxy (“CBE”) and atomic layer deposition(“ALD”). Chemical vapor deposition processes, such as metalorganicchemical vapor deposition (“MOCVD”), deposit a metal layer bydecomposing organometallic precursor compounds at elevated temperatures,i.e., above room temperature, either atmospheric pressure or at reducedpressures. A wide variety of metals may be deposited using such CVD orMOCVD processes.

For semiconductor and electronic device applications, theseorganometallic precursor compounds must be highly pure and besubstantially free of detectable levels of both metallic impurities,such as silicon and zinc, as well as oxygenated impurities. Oxygenatedimpurities are typically present from the solvents used to prepare suchorganometallic compounds, and are also present from other adventitioussources of moisture or oxygen.

For certain applications where high speed and frequency response of anelectronic device is desired, silicon-only devices, e.g. silicon bipolartransistors, have not been competitive. In a heterojunction bipolartransistor (“HBT”), a thin silicon-germanium layer is grown as the baseof a bipolar transistor on a silicon wafer. The silicon-germanium HBThas significant advantages in speed, frequency response, and gain whencompared to a conventional silicon bipolar transistor. The speed andfrequency response of a silicon-germanium HBT are comparable to moreexpensive gallium-arsenide HBTs.

The higher gain, speeds, and frequency response of silicon-germaniumHBTs have been achieved as a result of certain advantages ofsilicon-germanium not available with pure silicon, for example, narrowerband gap and reduced resistivity. Silicon-germanium may be epitaxiallygrown on a silicon substrate using conventional silicon processing andtools. This technique allows one to engineer device properties such asthe energy band structure and carrier mobility. For example, it is knownin the art that grading the concentration of germanium in thesilicon-germanium base builds into the HBT device an electric field orpotential gradient, which accelerates the carriers across the base,thereby increasing the speed of the HBT device compared to asilicon-only device. A common method for fabricating silicon andsilicon-germanium devices is by CVD. A reduced pressure chemical vapordeposition technique (“RPCVD”) used to fabricate the HBT device allowsfor a controlled grading of germanium concentration across the baselayer as well as precise control over the doping profile.

Germane (GeH₄) is the conventional precursor for germanium depositionwhile silane (SiH₄), and dichlorosilane (SiH₂Cl₂) are conventionalprecursors for silicon deposition. These precursors are difficult tohandle and have high vapor pressures. For example, germane decomposesviolently at 280° C., which is below the temperature used to growgermanium films. Accordingly, processes employing either germane orsilane require extensive safety procedures and equipment. Germanetypically requires film growth temperatures of approximately 500° C. orhigher for thermal CVD applications. Such decomposition temperatures arenot always suitable, such as in mass production applications where thereis a need for lower temperatures, e.g. 200° C. Other CVD applicationsrequire higher growth temperatures which cause conventional precursorsto break up prematurely which, in turn, leads to the formation ofparticles and a reduction in metal film growth rates. A further problemwith conventional silicon and germanium precursors is that when arelatively stable silicon precursor and a relatively unstable germaniumprecursor are used to deposit a silicon-germanium film, the differencesin precursor stability makes control of the silicon-germaniumcomposition difficult. There is a need for precursors for silicon andgermanium vapor phase deposition that are safer to handle and havedecomposition temperatures tailored to specific conditions. There isalso a desire for silicon and germanium precursors that have matchedstability characteristics.

SUMMARY OF THE INVENTION

The present inventors have surprisingly found that the abovedeficiencies can be remedied. The present invention provides a method ofdepositing a metal-containing film on a substrate including the stepsof: a) conveying one or more of the organometallic compounds of formulaI in a gaseous phase to a deposition chamber containing the substrate,

wherein M is Si or Ge; R¹ and R² are independently chosen from H, alkyl,alkenyl, alkynyl and aryl; each R³ is independently chosen from(C₁-C₁₂)alkyl, alkenyl, alkynyl and aryl, provided that R³ is notcyclopentadienyl; each R⁴ is independently chosen from (C₃-C₁₂)alkyl; Xis halogen; a=0-3; b=0-3; c=0-3; d=0-3; e=0-4; and a+b+c+d+e=4; whereinR³≠R⁴; wherein the sums of a+b and a+d are each ≦3; provided that whenM=Si the sum of b+c is ≦3; b) decomposing the one or more organometalliccompounds in the deposition chamber; and c) depositing the metal film onthe substrate.

Also, the present invention provides a device for feeding a fluid streamsaturated with an organometallic compound suitable for depositing ametal film containing silicon, germanium and combinations thereof to achemical vapor deposition system including a vessel having an elongatedcylindrical shaped portion having an inner surface having across-section, a top closure portion and a bottom closure portion, thetop closure portion having an inlet opening for the introduction of acarrier gas and an outlet opening, the elongated cylindrical shapedportion having a chamber containing one or more organometallic compoundsof formula I

wherein M is Si or Ge; R¹ and R² are independently chosen from H, alkyl,alkenyl, alkynyl and aryl; each R³ is independently chosen from(C₁-C₁₂)alkyl, alkenyl, alkynyl and aryl, provided that R³ is notcyclopentadienyl; each R⁴ is independently chosen from (C₃-C₁₂)alkyl; Xis halogen; a=0-3; b=0-3; c=0-3; d=0-3; e=0-4; and a+b+c+d+e=4; whereinR³≠R⁴; wherein the sums of a+b and a+d are each ≦3; provided that whenM=Si the sum of b+c is ≦3; the inlet opening being in fluidcommunication with the chamber and the chamber being in fluidcommunication with the outlet opening.

Another embodiment of the present invention is an apparatus for vapordeposition of metal films including one or more devices for feeding afluid stream including one or more organometallic compounds describedabove.

The present invention further provides an organogermanium compound offormula IIA or IIB:

wherein R¹ and R² are independently chosen from alkyl, alkenyl, alkynylor aryl; each R³ is independently chosen from (C₁-C₁₂)alkyl, alkenyl,alkynyl and aryl; each R⁴ is independently chosen from branched andcyclic (C₃-C₅)alkyl; each R⁵ is independently chosen from (C₁-C₁₂)alkyl,alkenyl, alkynyl and aryl; X is halogen; a′=0-3; b′=0-2; c′=1-3; d′=0-3;a′+b′+c′+d′=4; a″=0-2; b″=0-2; e″=1-2; f″=0-2; a″+b″+e″+f″=4; wherein atleast two of a″, b″ and f″≠0; provided when a″=1, e″=1, f″=2, andR⁴=(CH₃)C that R⁵≠CH₃; and provided that R³ is branched or cyclic(C₃-C₅)alkyl when c′+d′=4.

In further embodiment, the present invention provides a method ofdepositing a germanium-containing film on a substrate comprising thesteps of: a) conveying one or more of the organogermanium compoundsdescribed above in a gaseous phase to a deposition chamber containingthe substrate; b) decomposing the one or more organogermanium compoundsin the deposition chamber; and c) depositing the germanium-containingfilm on the substrate.

Further, the present invention provides a method of manufacturing anelectronic device including the step of depositing agermanium-containing film on a substrate wherein the film is depositedby the steps of: a) conveying one or more of the organogermaniumcompounds described above in a gaseous phase to a deposition chambercontaining the substrate; b) decomposing the one or more organogermaniumcompounds in the deposition chamber; and c) depositing thegermanium-containing film on the substrate.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification, the following abbreviations shallhave the following meanings, unless the context clearly indicatesotherwise: ° C.=degrees centigrade; NMR=nuclear magnetic resonance;mol=moles; b.p.=boiling point, g=gram; L=liter; M=molar;ca.=approximately; μm=micron=micrometer; cm=centimeter; ppm=parts permillion; and mL=milliliter.

“Halogen” refers to fluorine, chlorine, bromine and iodine and “halo”refers to fluoro, chloro, bromo and iodo. Likewise, “halogenated” refersto fluorinated, chlorinated, brominated and iodinated. “Alkyl” includeslinear, branched and cyclic alkyl. Likewise, “alkenyl” and “alkynyl”include linear, branched and cyclic alkenyl and alkynyl, respectively.The term “SiGe” refers to silicon-germanium. The articles “a” and “an”refer to the singular and the plural. As used herein, “CVD” is intendedto include all forms of chemical vapor deposition such as MOCVD, MOVPE,OMVPE, OMCVD and RPCVD.

Unless otherwise noted, all amounts are percent by weight and all ratiosare molar ratios. All numerical ranges are inclusive and combinable inany order except where it is clear that such numerical ranges areconstrained to add up to 100%.

In one embodiment, the present invention relates to organometalliccompounds of formula I:

wherein M is Si or Ge; R¹ and R² are independently chosen from H, alkyl,alkenyl, alkynyl and aryl; each R³ is independently chosen from(C₁-C₁₂)alkyl, alkenyl, alkynyl and aryl, provided that R³ is notcyclopentadienyl; each R⁴ is independently chosen from (C₃-C₁₂)alkyl; Xis halogen; a=0-3; b=0-3; c=0-3; d=0-3; e=0-4; and a+b+c+d+e=4; whereinR³≠R⁴; wherein the sums of a+b and a+d are each ≦3; provided that whenM=Si the sum of b+c is ≦3. In one embodiment, M=Ge. In anotherembodiment, c>0. In a further embodiment, c>0 and b>0. Typically, d=0-2.Particularly suitable organometallic compounds where M=Si are thosewherein a=0-2, b=0-2, c=1-2, and d=0-2, and more particularly two of a,b and are not 0.

Particularly suitable organometallic compounds are the organogermaniumcompounds of formulae IIA and IIB:

wherein R¹ and R² are independently chosen from alkyl, alkenyl, alkynylor aryl; each R³ is independently chosen from (C₁-C₁₂)alkyl, alkenyl,alkynyl and aryl; each R⁴ is independently chosen from branched andcyclic (C₃-C₅)alkyl; each R⁵ is independently chosen from (C₁-C₁₂)alkyl,alkenyl, alkynyl and aryl; X is halogen; a′=0-3; b′=0-2; c′=1-3; d=′0-3;a′+b′+c′+d′=4; a″=0-2; b″=0-2; e″=1-2; f″=0-2; a″+b″+e″+f″=4; wherein atleast two of a″, b″ and f″≠0; provided when a″=1, e″=1, f″=2, andR⁴═(CH₃)C that R⁵≠CH₃; and provided that R³ is branched or cyclic(C₃-C₅)alkyl when c′+d′=4. In one embodiment, R³ is branched or cyclic(C₃-C₅)alkyl. Suitable compounds of formula IIA are those whereind′=1-3. Other suitable compounds of formula IIA are those whereinb′=1-2. Particularly suitable compounds are those wherein d′=1-3 andb′=1-2. Typically, R¹ and R² are independently chosen from methyl, ethyland propyl. In another embodiment, f″=1-2. Still further, b″=1-2.Particularly suitable compounds of formula IIB are those wherein f″=1-2and b″=1-2. R⁴ is a bulky group and is typically tert-butyl, iso-propyl,iso-butyl, sec-butyl, neopentyl, and cyclopentyl. The bulky groupspreferably are those capable of undergoing β-hydride elimination. Thus,preferred bulky groups contain a hydrogen bonded to the carbon in thebeta position to the germanium.

Typical dialkylamino (NR¹R²) groups include, but are not limited to,dimethylamino, diethylamino, di-iso-propylamino, ethylmethylamino,iso-propylamino, and tert-butylamino. X may be F, Cl, Br or I.Typically, X is Cl or Br. When two or more halogens are present, suchhalogens may be the same or different.

A wide variety of alkyl, alkenyl and alkynyl groups may be used for R¹,R², R³ and R⁵. Suitable alkyl groups include, without limitation,(C₁-C₁₂)alkyl, typically (C₁-C₆)alkyl and more typically (C₁-C₄)alkyl.Exemplary alkyl groups include methyl, ethyl, n-propyl, iso-propyl,n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, cyclopentyl, hexyl,and cyclohexyl. More typically, suitable alkyl groups include ethyl,iso-propyl, and tert-butyl. Suitable alkenyl groups include, withoutlimitation, (C₂-C₁₂)alkenyl, typically (C₂-C₆)alkenyl and more typically(C₂-C₄)alkenyl. Exemplary alkenyl groups include vinyl, allyl, methallyland crotyl. Typical alkynyl groups include, without limitation,(C₂-C₁₂)alkynyl, typically (C₂-C₆)alkynyl and more typically(C₂-C₄)alkynyl. Suitable aryl groups are (C₆-C₁₀)aryl, including, butnot limited to, phenyl, tolyl, xylyl, benzyl and phenethyl. When two ormore alkyl, alkenyl or alkynyl groups are present, such groups may bethe same or different.

Any of the above alkyl, alkenyl, alkynyl or aryl groups of R¹, R², R³and R⁵ may optionally be substituted, such as with halogen. By“substituted” it is meant that one or more hydrogens on the alkyl,alkenyl, alkynyl or aryl group is replaced with one or more halogens.

Organometallic compounds exemplary of formula I include, but are notlimited to, dichloro bis(dimethylamino) silane, chlorotris(dimethylamino) silane, dimethylamino silane, bis(dimethylamino)silane, iso-propyl (diethylamino) silane, tert-butyl silane,di-tert-butyl silane, iso-propyl silane, di-isopropyl silane, tert-butyl(methyl) silane, tert-butyl (methyl) (dichloro) silane, iso-propyl(dimethylamino) silane, iso-propyl bis(dimethylamino) silane,di-iso-propyl (dimethylamino) silane, tert-butyl (trichloro) silane,di-tert-butyl (dibromo) silane, cyclopropyl silane, cyclopropyl(dimethyl) silane, cyclopentyl (dimethylamino) silane, tert-butyl(trimethyl) germane, iso-propyl (trimethyl) germane, dimethyl germaniumchloride, tert-butyl germane, iso-propyl germane, tert-butyl (trichloro)germane, iso-propyl (tribromo) germane, n-butyl germane, tri-iso-propylgermane, benzyl germane, benzyl (methyl) germane, iso-butyl germane,iso-butyl (trichloro) germane and mixtures thereof.

Exemplary organogermanium compounds of formula IIA include, withoutlimitation, iso-propyl (dimethylamino) germane, di-iso-propyl(dimethylamino) germane, iso-propyl bis(dimethylamino) germane,iso-propyl (dimethylamino) germanium dichloride, tert-butyl(dimethylamino) germane, di-tert-butyl (dimethylamino) germane,tert-butyl bis(dimethylamino) germane, cyclopentyl (dimethylamino)germane, cyclopentyl (diethylamino) germane, methyl (dimethylamino)germane, methyl (dimethylamino) germanium dichloride, methyl(dimethylamino) germanium dibromide, methyl bis(di-iso-propylamino)germanium chloride, bis(diethylamino) germane, dichloro (diethylamino)germane, ethyl (diethylamino) germane, dichloro (ethyl) (diethylamino)germane, tert-butyl (diethylamino) germane, dichloro (tert-butyl)(diethylamino) germane, cyclopentadienyl (dimethylamino) germane,cyclopentadienyl bis(dimethylamino) germane, cyclopentadienyl(diethylamino) germane, cyclopentadienyl bis(diethylamino) germane,di-iso-propyl bis(dimethylamino) germane, dichloro bis(dimethylamino)germane, methyl bis(di-iso-propylamino) germane, di-iso-propylbis(diethylamino) germane, bromo (dimethyl) (dimethylamino) germane,bis(dimethylamino) germane, tris(dimethylamino)germane, vinyltris(dimethylamino) germane, divinyl (dimethylamino) germane, fluoro(divinyl) (dimethylamino) germane, benzyl (diethylamino) germane,dibenzyl (diethylamino) germane, di-iso-propyl (dimethylamino) germane,benzyl (dimethylamino) germane, and mixtures thereof.

Exemplary organogermanium compounds of formula IIB include, withoutlimitation, tert-butyl (dichloro) germane, di-tert-butyl germane,iso-propyl (chloro) germane, di-iso-propyl (dichloro) germane,tert-butyl (methyl) germane, tert-butyl (ethyl) germane, tert-butyl(dimethyl) germane, iso-propyl (methyl) germane, di-iso-propyl(dimethyl) germane, dichloro (methyl) (iso-propyl) germane, neo-pentyl(methyl) germane, neo-pentyl (dimethyl) germane, neo-pentyl (methyl)(dichloro) germane, cyclopropyl (methyl) germane, dicyclopropyl germane,di-iso-propyl germane, cyclopropyl (methyl) (dichloro) germane, dibromo(methyl) (tert-butyl) germane, cyclopentyl (dichloro) (methyl) germane,cyclopentyl (dichloro) germane, cyclopentyl (ethyl) (dibromo) germane,diethyl (tert-butyl) (fluoro) germane, and mixtures thereof.

The above-described organometallic compounds are particularly suitablefor use as precursors for CVD of films containing silicon, germanium andcombinations thereof.

The present organometallic compounds may be prepared by a variety ofprocedures. Typically, the organometallic compounds of the presentinvention are prepared starting from a compound of the formula MY₄ whereM is silicon or germanium and Y is a reactive group such as a halogen,an acetate or a (C₁-C₄)alkoxy, with halogens being most typical. As usedherein, a reactive group is any group attached to the metal that isdisplaced or exchanged in a subsequent reaction. The preparation of thepresent organometallic compounds will be described with respect togermanium precursors for purposes of illustration, however, suchpreparation is equally applicable to silicon, as well as other Group IVelements.

Dialkylamino-substituted organometallic compounds of the presentinvention may be prepared by the reaction of a dialkylamine in liquid orgaseous forms with a metal compound having one or more reactive groupsand more typically is prepared by the reaction of a dialkylamino lithiumreagent with such metal having one or more reactive groups. Suchreactions are typically performed in a hydrocarbon solvent, such as butnot limited to hexane, heptane, octane, nonane, decane, dodecane,toluene, and xylene. Preferably, such solvents are deoxygenated prior touse. The solvents may be deoxygenated by a variety of means, such aspurging with an inert gas, degassing the solvent in vacuo, or acombination thereof. Suitable inert gases include argon, nitrogen andhelium, and preferably argon or nitrogen. For example, germaniumtetrachloride may be reacted with a sufficient amount of dialkylaminolithium reagent to provide a desired dialkylamino germanium halidecompound. This reaction is illustrated in Equation 1.2 LiNMe₂+GeCl₄→(NMe₂)₂GeCl₂+2 LiCl  (1)

Alkyl, alkenyl, alkynyl and aryl substituted organometallic compoundsmay be prepared using Grignard or organolithium reactions. Suchreactions are well known to those skilled in the art. In a typicalGrignard reaction, a compound having one or more reactive groups isreacted with a Grignard reagent, such as methyl magnesium bromide orallyl magnesium bromide in an ethereal solvent. Typical etherealsolvents include, without limitation, diethyl ether, di-isopropyl ether,n-butyl ether, iso-pentyl ether, dihexyl ether, diheptyl ether,tetrahydrofuran, dioxane, monoglyme, diglyme, diethylene glycol dibutylether, diethylene glycol monobutyl ether, ethylene glycol dibutyl ether,ethylene glycol monohexyl ether, ethylene glycol monobenzyl ether,tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether,butyl phenyl ether, and dicyclohexyl ether. Such solvents are typicallydeoxygenated prior to use as described above. This reaction isillustrated in Equation 2.(NMe₂)₂GeCl₂+AllylMgBr→(NMe₂)₂Ge(Allyl)Cl+MgBrCl  (2)

In a typical organolithium reaction, a compound having one or morereactive groups is reacted with an organolithium reagent, such as methyllithium, tert-butyl lithium, n-butyl lithium and phenyl lithium in asuitable hydrocarbon or ethereal solvent. Suitable solvents are thosedescribed above for the dialkylamino lithium reaction. Equation 3illustrates the reaction of bis(dimethylamino)-germanium dichloride withiso-propyl lithium.(NMe₂)₂GeCl₂+i-PrLi→(NMe₂)₂Ge(i-Pr)Cl+LiCl  (3)

In another embodiment, a compound having two or more reactive groups maybe reacted with two different lithium reagents in one pot. Suchdifferent lithium reagents may be two different organolithium reagents,two different dialkylamino lithium reagents or a mixture of anorganolithium reagent and a dialkylamino lithium reagent. In suchreaction, the different lithium reagents may be added to the reactionsimultaneously or in a stepwise manner. Equation 4 illustrates thisreaction sequence for the reaction of germanium tetrachloride withtert-butyl lithium and dimethylamino lithium.t-BuLi+GeCl₄+LiNMe₂→(NMe₂)(tBu)GeCl₂+2LiCl  (4)

In a further embodiment, the alkyl-, alkenyl-, alkynyl- andaryl-substituted germanes may be prepared by a transalkylation reactionusing the appropriately substituted aluminum compound. For example,methyl-substituted germanes may be prepared by the reaction of anappropriate amount of trimethylaluminum with an appropriate amount ofgermanium tetrachloride in the presence of a tertiary amine. Suchamounts are well within the ability of those skilled in the art.Equation 5 illustrates this reaction sequence for the reaction ofgermanium tetrachloride with trimethylaluminum.GeCl₄+AlMe₃→Me₃GeCl+AlCl₃  (5)

Such transalkylation reactions using alkyl aluminum compounds arepreferably performed in the presence of a tertiary amine. Any tertiaryamine may suitably be used. Exemplary tertiary amines include, but arenot limited to, those having the general formula NR′R″R′″, wherein R″,R″ and R′″ are independently selected from (C₁-C₆)alkyl,di(C₁-C₆)alkylamino-substituted (C₁-C₆) alkyl, and phenyl and wherein R′and R″ may be taken together along with the nitrogen to which they areattached to form a 5-7 membered heterocyclic ring. Such heterocyclicring may be aromatic or non-aromatic. Particularly suitable tertiaryamines include, but are not limited to, trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-iso-propylamine,tri-iso-butylamine, dimethylaminocyclohexane, diethylaminocyclohexane,dimethylaminocyclopentane, diethylaminocyclopentane, N-methlpyrrolidine,N-ethylpyrrolidine, N-n-propylpyrrolidine, N-iso-propylpyrrolidine,N-methylpiperidine, N-ethylpiperidine, N-n-propylpiperidine,N-iso-propylpiperidine, N,N′-dimethylpiperazine, N,N′-diethylpiperazine,N,N′-dipropylpiperazine, N,N,N′,N′-tetramethyl-1,2-diaminoethane,pyridine, pyrazine, pyrimidine, and mixtures thereof. Preferred aminesinclude trimethylamine, triethylamine, tri-n-propylamine,triiso-propylamine, and tri-n-butylamine. More preferably, the tertiaryamine is triethylamine or tri-n-propylamine. It will be appreciated bythose skilled in the art that more than one tertiary amine may be usedin the present invention. Such tertiary amines are generallycommercially available from a variety of sources. Such tertiary aminesmay be used as is or, preferably further purified prior to use.

Germanes containing one or more Ge—H bonds can be prepared by thereduction of a germanium halide. In general, such reduction is performedin a dried organic solvent which has been deoxygenated as describedabove. A wide variety of organic solvents are suitable. A wide varietyof reducing agents may be used in the present invention. Particularlyuseful reducing agents include reactive metals; hydrides such as sodiumhydride and lithium hydride; borohydride reducing agents such as sodiumborohydride and lithium borohydride; aluminum hydride reducing agentssuch as lithium aluminum hydride and NaAlH₂(OCH₂CH₂OCH₃)₂; boranereducing agents such as dimethylamine borane, cyclohexylamine borane,morpholine borane, and the like. In another embodiment, such reductionstep may be performed in the presence of a tertiary amine. In suchreaction, the tertiary amine, organic solvent and reducing agent may becombined in any order prior to reacting with the germanium halide.Suitable temperatures for forming the germanes of the present inventionare from below ambient temperature to 90° C. This reduction reaction isillustrated in Equations 6 and 7.(NMe₂)₂Ge(Allyl)Cl+LiAlH₄→(NMe₂)₂Ge(Allyl)H  (6)(NMe₂)(tBu)GeCl₂+LiAlH₄→(NMe₂)(tBu)GeH₂  (7)

In each of the above described reactions, the mole ratio of reagent tothe metal compound depends upon the number of reactive groups in themetal compound that are to be exchanged. Typically, the mole ratio ofany of the above reagents to the reactive group is from 1:1 to 1.3:1.Accordingly, if two reactive groups in the metal compound are to beexchanged, the mole ratio of reagent to metal compound is from 2:1 to2.6:1, which corresponds to a mole ratio of reagent to reactive group of1:1 to 1.3:1. Other amounts and ratios may be used depending upon thespecific reaction conditions employed.

It will be appreciated by those skilled in the art that the order of theabove reactions may be performed in any order. Typically, any step ofreducing a metal-halide compound to form a metal-hydrogen compound willbe performed last, although other orders of reaction may beadvantageous.

Any of the above described methods of preparing the desiredorganometallic precursor compounds may be performed in a batch,semi-batch, continuous or semi-continuous mode. For example, the presentinvention provides a batch as well as semi-continuous process for thepreparation of organometallic compounds of Group IV, including the stepsof delivering a Group IV metal compound and alkylating agentindependently to a reaction zone maintained at a predeterminedtemperature sufficient to allow the alkylation to proceed and theproduct is then separated once the reaction is complete. Theorganometallic product is collected at the outlet preferably located atthe top of the reactor while the byproduct in non-vaporized state isremoved as waste from the reactor at the end of the reaction. Theaddition of reagents in a multi-step alkylation may be either in asimultaneous or sequential manner. The rate of addition of the variousreagents may be controlled by using appropriate flow controllers thatare known in the art.

In another embodiment, the present invention also provides a continuousprocess for the preparation of organometallic compounds of Group IV,including the steps of delivering a Group IV metal compound andalkylating agent independently to a reaction zone maintained atpredetermined temperature sufficient to allow the alkylation to proceedand the product to vaporize. The organometallic product is thencollected at the outlet preferably located at the top of the reactorwhile the byproduct in non-vaporized state is removed as waste from thebase of the reaction zone. The continuous operation to deliverorganometallic compound may be controlled by continuous transfers of thereagents to the reaction zone, their delivery rates, the vapor-liquidequilibrium established between the vapor of the product moving upwardand the liquid byproduct moving downward, the take-off rate of theproduct at the outlet of the reaction zone, and the rate of removal ofthe byproduct waste from the base of the reaction zone.

In a further embodiment, the present invention also provides acontinuous process for the preparation of organometallic hydrides ofGroup IV, including the steps of delivering a Group IV metal halide andreducing agent independently to a reaction zone maintained atpredetermined temperature sufficient to allow the reduction to proceedand the product to evaporate. The organometallic product is thencollected at the outlet preferably located at the top of the reactorwhile the byproduct in non-vaporized state is removed as waste from thebase of the reaction zone. The continuous operation to deliverorganometallic compound may be controlled by the continuous transfers ofthe reagents to the reaction zone, their delivery rates, thevapor-liquid equilibrium established between the vapor of the productmoving upward and the liquid byproduct moving downward, the take-offrate of the product at the top outlet of the reaction zone, and the rateof removal of the byproduct waste from the base of the reaction zone.

An advantage of the present invention is that the present organometalliccompounds are substantially free of metallic impurities such as zinc andaluminum, and preferably free of zinc and aluminum. In particular, thepresent organogermanium compounds are substantially free of zinc,aluminum and silicon, and preferably free of such impurities. By“substantially free” it is meant that the compounds contain less than0.5 ppm of such impurities, and preferably less than 0.25 ppm. Inanother embodiment, the present organometallic compounds have “5-nines”purity, i.e. a purity of ≧99.999%. More typically, the present compoundshave a purity of “6-nines”, i.e. ≧99.9999%. Certain of these compoundsare typically liquids at room temperature and provide safer alternativesthan conventional silicon and germanium precursors for vapor phasedeposition.

The present organometallic compounds are particularly suitable for useas precursors in all vapor deposition methods such as LPE, MBE, CBE, ALDand CVD, and particularly MOCVD and metalorganic vapor phase epitaxy(“MOVPE”). More particularly, the present organometallic compounds aresuitable for use as precursors in the vapor phase deposition ofsilicon-germanium (“SiGe”) films. Such films are useful in themanufacture of electronic devices, such as integrated circuits, andoptoelectronic devices, and particularly in the manufacture ofheterojunction bipolar transistors.

Films of silicon, germanium, and combinations thereof are typicallydeposited by first placing the desired organometallic precursorcompound, i.e. source compound, in a delivery device, such as acylinder, having an outlet connected to a deposition chamber. A widevariety of cylinders may be used, depending upon the particulardeposition apparatus used. When the precursor compound is a solid, thecylinders disclosed in U.S. Pat. No. 6,444,038 (Rangarajan et al.) andU.S. Pat. No. 6,607,785 (Timmons et al.), as well as other designs, maybe used. For liquid precursor compounds, the cylinders disclosed in U.S.Pat. Nos. 4,506,815 (Melas et al) and 5,755,885 (Mikoshiba et al) may beused, as well as other liquid precursor cylinders. The source compoundis maintained in the cylinder as a liquid or solid. Solid sourcecompounds are typically vaporized or sublimed prior to transportation tothe deposition chamber.

Accordingly, the present invention provides a device for feeding a fluidstream saturated with an organometallic compound suitable for depositinga metal film containing silicon, germanium, and combinations thereof toa chemical vapor deposition system including a vessel having anelongated cylindrical shaped portion having an inner surface having across-section, a top closure portion and a bottom closure portion, thetop closure portion having an inlet opening for the introduction of acarrier gas and an outlet opening, the elongated cylindrical shapedportion having a chamber containing one or more organometallic compoundsof formula I

wherein M is Si or Ge; R¹ and R² are independently chosen from H, alkyl,alkenyl, alkynyl and aryl; each R³ is independently chosen from(C₁-C₁₂)alkyl, alkenyl, alkynyl and aryl, provided that R³ is notcyclopentadienyl; each R⁴ is independently chosen from (C₃-C₁₂)alkyl; Xis halogen; a=0-3; b=0-3; c=0-3; d=0-2; e=0-4; and a+b+c+d+e=4; whereinR³≠R⁴; wherein the sums of a+b and a+d are each ≦3; provided that whenM=Si the sum of b+c is ≦3; the inlet opening being in fluidcommunication with the chamber and the chamber being in fluidcommunication with the outlet opening.

In a still further embodiment, the present invention provides anapparatus for chemical vapor deposition of metal films including one ormore devices for feeding a fluid stream saturated with one or moreorganometallic compounds described above.

The source compound is typically transported to the deposition chamberby passing a carrier gas through the cylinder. Suitable carrier gassesinclude nitrogen, hydrogen, and mixtures thereof. In general, thecarrier gas is introduced below the surface of the source compound, andpasses up through the source compound to the headspace above it,entraining or carrying vapor of the source compound in the carrier gas.The entrained or carried vapor then passes into the deposition chamber.

The deposition chamber is typically a heated vessel within which isdisposed at least one, and possibly many, substrates. The depositionchamber has an outlet, which is typically connected to a vacuum pump inorder to draw by-products out of the chamber and to provide a reducedpressure where that is appropriate. MOCVD can be conducted atatmospheric or reduced pressure. The deposition chamber is maintained ata temperature sufficiently high to induce decomposition of the sourcecompound. The deposition chamber temperature is from 200° to 1200° C.,the exact temperature selected being optimized to provide efficientdeposition. Optionally, the temperature in the deposition chamber as awhole can be reduced if the substrate is maintained at an elevatedtemperature, or if other energy such as radio frequency (“RF”) energy isgenerated by an RF source.

Suitable substrates for deposition, in the case of electronic devicemanufacture, may be silicon, gallium arsenide, indium phosphide, and thelike. Such substrates may contain one or more additional layers ofmaterials, such as, but not limited to, dielectric layers and conductivelayers such as metals. Such substrates are particularly useful in themanufacture of electronic devices, such as integrated circuits.

Deposition is continued for as long as desired to produce a film havingthe desired properties. Typically, the film thickness will be fromseveral hundred angstroms to several tens of nanometers to severalhundreds of microns or more when deposition is stopped.

Thus, the present invention provides a method for depositing ametal-containing film a substrate including the steps of: a) conveyingone or more organometallic source compounds of formula I in the gaseousphase to a deposition chamber containing the substrate; b) decomposingthe one or more organometallic source compounds in the depositionchamber; and c) depositing the metal-containing film the substrate,wherein the metal-containing film includes silicon, germanium andcombinations thereof. The organogermanium compounds of formulae ILIA andIIB may be suitably used in such method.

The present invention further provides a method for manufacturing anelectronic device including the step of depositing a film containingsilicon, germanium, and combinations thereof on an electronic devicesubstrate including the steps of: a) conveying one or moreorganometallic source compounds of formula I in the gaseous phase to adeposition chamber containing the substrate; b) decomposing the one ormore organometallic source compounds in the deposition chamber; and c)depositing a film containing silicon, germanium and combinations thereofon the substrate. In an alternate embodiment, organogermanium compoundsof formulae IIA and IIB may be used in such method.

The present invention is particularly suitable for the deposition ofsilicon-containing films, germanium-containing films and SiGe films.SiGe films are being employed for two technologies. One well-establishedmajor application is Bipolar CMOS or BiCMOS where a thin (40 to 80 nm)SiGe film is used as the base of a high frequency HBT. The substrate forthe deposition of this SiGe base film and the subsequent Si collectorfilm is a highly structured silicon wafer with the CMOS circuitry mostlyfinished. The other application for SiGe CVD is the area of strainedsilicon or s-Si. Here a deposition of a thick 3 to 5 micrometer SiGelayer takes place on a plain silicon wafer. Subsequent to the growth ofthe SiGe film a thin (20 nm) Si film is grown. This silicon film adoptsthe crystal lattice of the underlying SiGe layer (strained silicon).Strained silicon shows much faster electrical responses than regularsilicon.

In another embodiment, a method for fabricating a device containing agroup of silicon-germanium layers is illustrated by the steps of: i)providing a substrate including a surface layer of a group IV element,ii) maintaining the substrate at a temperature ranging from 400° C. to600° C., iii) forming a layer of Si_(1-x)Ge_(x), where x ranges from 0to 0.50, on the substrate by MOCVD using any of the above-describedsilicon and germanium precursors; iv) maintaining the substrate at aboutthe temperature of step i) and continuing the silicon precursor flowwith the germanium precursor flow completely switched off, in order toobtain abrupt interfaces, and v) maintaining the substrate at about thetemperature of step i), and forming a cap layer of strained silicon,thereby improving the mobility of electrons and speed of the device.

The following examples are expected to further illustrate variousaspects of the present invention, but are not intended to limit thescope of the invention in any aspect. All manipulations are performed inan inert atmosphere, typically under an atmosphere of dry nitrogen.

EXAMPLE 1

Dimethylamino germanium trichloride is expected to be synthesizedaccording to the equation:LiNMe₂+GeCl₄→(NMe₂)GeCl₃+LiCl

To a stirred solution of germanium tetrachloride (50 g, 0.233 moles) inpentane (100 mL) maintained at 0° C., is added dropwise a solution oflithium dimethylamide in diethyl ether (11.898 g, 0.233 moles, 50 mL)via pressure equalized addition funnel. The addition lasts forapproximately 30 minutes. When the addition is completed, the resultingmixture is allowed to slowly warm to room temperature after which asuspension is expected to be obtained.

When the suspension settles, the supernatant mother liquor is separatedusing a siphon technique. The precipitate of lithium chloride byproductis washed with fresh pentane and the washings are separated via siphonunder nitrogen atmosphere, and are subsequently combined with the motherliquor. The pentane/ether solvents are then removed via atmosphericpressure distillation by heating the reaction mass to 60° C. Theexpected crude product obtained may be further purified by vacuumdistillation and is expected to yield high purity dialkylamino germaniumtrichloride free of metallic impurities and organic solvents.

EXAMPLE 2

The procedure of Example 1 is repeated except that silicon tetrachlorideis used instead of germanium tetrachloride and is expected to preparedialkylamino silicon trichloride. The product is expected to have totalmetallic impurities of <5 ppm.

EXAMPLE 3

Ethyl germanium trichloride is expected to be synthesized according tothe equation:EtMgBr+GeCl₄→EtGeCl₃+MgBrCl

To a stirred solution of germanium tetrachloride (50 g, 0.233 moles) indiethylether (100 mL) maintained at 0° C., is added dropwise a solutionof ethylmagnesium bromide in diethyl ether (0.233 moles, 78 mL of 3.0 M)via pressure equalized addition funnel. This addition lasts forapproximately 45 minutes. When the addition is completed, the resultingmixture is allowed to slowly warm to room temperature after which asuspension is expected to be obtained.

When the suspension settles, the supernatant mother liquor is separatedusing a siphon technique. The expected precipitate of magnesium halidebyproduct is washed with fresh diethylether and the washings areseparated via siphon under nitrogen atmosphere, and are subsequentlycombined with the mother liquor. The ether solvent is then removed viaatmospheric pressure distillation to leave the expected crude product.The reaction mixture is then heated to 50 to 60° C. using an oil bath.The crude product may be further purified via fractional distillationand is expected to yield high purity ethyl germanium trichloride free ofmetallic impurities and organic solvents.

EXAMPLE 4

The procedure of Example 3 is repeated except that silicon tetrachlorideis used instead of germanium tetrachloride and is expected to provideethyl silicon trichloride.

EXAMPLE 5

Ethyl germanium trichloride is expected to be synthesized according tothe equation:LiEt+GeCl₄→EtGeCl₃+LiCl

To a cool stirred solution of germanium tetrachloride (50 g, 0.233moles) in benzene (100 mL) maintained at 0° C., is added dropwise asolution of ethyllithium in benzene/cyclohexane (90:10) (0.25 moles, 500mL of 0.5 M) via pressure equalized addition funnel. This addition lastsfor approximately 60 minutes. When the addition is complete, theresulting mixture is allowed to slowly warm to room temperature afterwhich a suspension is expected. When the suspension settles, thesupernatant mother liquor is separated using a siphon technique. Theexpected precipitate of lithium halide byproduct is washed with freshcyclohexane and the washings are separated via siphon under nitrogenatmosphere, and are then subsequently combined with the mother liquor.The solvent mixture is then removed via atmospheric pressuredistillation to leave the expected crude product. The reaction mixtureis then heated to 50° to 60° C. using an oil bath. The expected crudeproduct may be further purified via its fractional distillation and isexpected to yield high purity ethyl germanium trichloride free ofmetallic impurities and organic solvents.

EXAMPLE 6

The procedure of Example 5 is repeated except that silicon tetrachlorideis used instead of germanium tetrachloride and is expected to provideethyl silicon trichloride.

EXAMPLE 7

Ethyl germane is expected to be synthesized according to the equation:EtGeCl₃+LiAlH₄→EtGeH₃+LiAlHCl₃

To a room temperature stirred suspension of excess reducing agent(either LiAlH₄ or NaBH₄, 0.5 moles) in n-butyl ether is added dropwiseEtGeCl₃ obtained from Example 5 (50 g, 0.240 moles) dissolved in n-butylether (100 mL) via pressure equalized dropping funnel under nitrogen. Anexpected exothermic reaction occurs yielding a gray suspension. Crudeproduct is distilled pot to pot under vacuum along with some n-butylether solvent. The expected final product is then isolated from n-butylether via fractional distillation.

EXAMPLE 8

Bis(dimethylamino) germane is expected to be synthesized according tothe equation:(NMe₂)₂GeCl₂+LiAlH₄→(NMe₂)₂GeH₂+LiAlH₂Cl₂

To a room temperature stirred suspension of excess reducing agent (0.5moles, either LiAlH₄ or NaBH₄) in n-butyl ether is added dropwise(NMe₂)₂GeCl₂ (0.2241 moles) dissolved in n-butyl ether via pressureequalized dropping funnel under nitrogen. An exothermic reaction isexpected yielding a gray-white suspension. The expected crude product isdistilled pot to pot under vacuum along with some n-butyl ether solvent.The expected final product may be isolated from n-butyl ether viafractional distillation.

EXAMPLE 9

The procedure of Example 8 is repeated except thatbis(dimethylamino)silicon dichloride is used instead ofbis(dimethylamino) germanium dichloride and is expected to providebis(dimethylamino)silane.

EXAMPLE 10

Dimethylamino ethyl germanium dichloride is expected to be synthesizedaccording to the equation:(NMe₂)GeCl₃+EtMgBr→(NMe₂)Ge(Et)Cl₂+MgClBr

To a low temperature stirred solution of (NMe₂)GeCl₃ (50 g, 0.2241moles) in diethyl ether (100 mL) is added dropwise EtMgBr in diethylether (0.23 moles) via pressure equalized dropping funnel undernitrogen. An exothermic reaction is expected yielding a suspension. Theexpected crude product is distilled from the mixture under full vacuumto yield product mixed with diethyl ether. The expected final product isobtained via fractional distillation at atmospheric pressure afterremoval of bulk diethyl ether solvent. The expected product may thenfurther purified by one more fractional distillation.

EXAMPLE 11

The procedure of Example 10 is repeated except that dimethylaminosilicon trichloride is used and is expected to provide dimethylaminoethyl silicon dichloride.

EXAMPLE 12

Dimethylamino ethyl germane is expected to be synthesized according tothe equation:(NMe₂)Ge(Et)Cl₂+LiAlH₄→(NMe₂)Ge(Et)H₂+LiAlH₂Cl₂

To a room temperature stirred suspension of excess reducing agent (0.5moles, either LiAlH₄ or NaBH₄) in n-butyl ether is added dropwise(NMe₂)(Et)GeCl₂ from Example 10 (50 g, 0.23 moles) dissolved in n-butylether via pressure equalized dropping funnel under nitrogen. Anexothermic reaction is expected yielding a gray suspension. The expectedcrude product is then distilled pot to pot under vacuum along with somen-butyl ether solvent. The expected final product may be isolated fromn-butyl ether via fractional distillation.

EXAMPLE 13

The compounds in the following Table are expected to be preparedaccording to one or more of the previous Examples. The abbreviations,“Et”, “Me” and “i-Pr” refer to “ethyl”, “methyl” and “iso-propyl”,respectively. The abbreviation “Ph” refers to a phenyl group.

Germanium Precursors Silicon Precursors (NMe₂)GeH₃ (NEt₂)(Me)SiH₂(NMe₂)₂GeH₂ (Ni—Pr₂)₂SiCl₂ (NMe₂)₃GeH (i-Pr)₃SiCl (CH₂═CH—CH₂)GeH₃(CH₂═CH—CH₂)SiH₃ (CH₂═CH—CH₂)₂GeH₂ (CH₂═CH—CH₂)₂SiH₂ (CH₂═CH—CH₂)₃GeH(CH₂═CH—CH₂)₃SiH (CH₂═CH)GeH₃ (CH₂═CH)SiH₃ (CH₂═CH)₂GeH₂(CH₂═CH)₂(Me₃C)SiH (CH₂═CH)₃GeH (CH₂═CH)₃SiH (CH₂═CH)Ge(NMe₂)₃(CH₂═CH)Si(NMe₂)₃ (CH₂═CH)₂Ge(NMe₂)₂ (CH₂═CH)₂Si(NMe₂)₂(CH₂═CH)₃Ge(NMe₂) (CH₂═CH)₃Si(NMe₂) (Ph—CH₂)GeH₃ (Ph—CH₂)SiH₃(Ph—CH₂)₂GeH₂ (Ph—CH₂)₂(Me)SiH (Ph—CH₂)₃GeH (Ph—CH₂)₃(NMe₂)Si (Me₃C)GeH₃(Me₃C)SiH₃ (Me₃C)₂GeH₂ (Me₃C)₂SiH₂ (Me₃C)₃GeH (Me₃C)₃SiCl(Me₃C)(NMe₂)GeH₂ (Me₃C)(NMe₂)SiH₂ (Me₂N)(i-Pr)GeH₂ i-PrSiH₃(Me)(Me₃C)GeH₂ (Et)(Me₃C)SiH₂ (i-Pr)₂GeH₂ (Me₂N)₂SiMe₂ (Me)₂(Me₃C)GeH(Me₂N—C₂H₄)₂SiH₂ (Me)(NMe₂)GeH₂ (Me₂N—C₃H₆)(NMe₂)SiH₂ (NMe₂)(Et)GeH₂(Me₂N—C₃H₆)(NMe₂)(Et)SiH (NMe₂)₂(Et)GeCl (Me₂N—C₃H₆)(NMe₂)(Et)SiCl(Me₃C)(NMe₂)GeCl₂ (Me₃C)(NMe₂)SiCl₂ (i-Pr)₂(NMe₂)GeCl (i-Pr)₂(NMe₂)SiCl

EXAMPLE 14

Tert-buylmethylgermane was synthesized according to the followingequation.CH₃GeCl₃+(CH₃)₃CMgCl→(CH₃)₃CGe(CH₃)Cl₂+MgCl₂(CH₃)₃CGe(CH₃)Cl₂+LiAlH₄→(CH₃)₃CGe(CH₃)H₂+LiAlH₂Cl₂

To a stirred solution of methylgermanium trichloride (52 g, 0.24 mol) inethyldiglyme (100 mL) maintained at below 40° C. was added dropwise asolution of tert-butylmagnesium chloride in butyl diglyme (0.275 mol,250 mL) via pressure equalized addition funnel. The addition lasted for180 minutes. When the addition was completed, the reaction mixture wasadded to a stirred mixture of lithium hydride (12 g) in ethyldiglyme(200 mL) using a transfer line in a dropwise manner. The crude product(16 g) was obtained by vacuum distillation at 32 mtorr and was confirmedby NMR to be the desired germane contaminated with solvent (NMR spectrumcontained a quadruplet at 3.82 ppm, a singlet at 1.00 ppm and a tripletat 0.14 ppm, corresponding to GeH₂, (CH₃)₃C and CH₃, respectively).

EXAMPLE 15

Trimethylpropylgermane was synthesized according to the followingequation.(CH₃)₃GeCl+C₃H₇MgCl→(CH₃)₃Ge(C₃H₇)+MgCl₂

To a stirred solution of trimethylgermanium chloride (120 g, 0.78 mol)in butyldiglyme (200 mL) maintained at below 40° C. was added dropwise asolution of n-propylmagnesium chloride in diethylether (0.780 mol, 390mL) via pressure equalized addition funnel. The addition lasted for 120minutes. When the addition was completed, the reaction mixture washeated to gentle reflux for two hours. The crude product was obtained byvacuum distillation and was confirmed by NMR to be the desired germane.The crude product was further purified via its fractional distillation(80 g, Yield=70%).

EXAMPLE 16

Trimethylisopropylgermane was synthesized according to the followingequation.(CH₃)₃GeCl+C₃H₇MgCl→(CH₃)₃Ge(C₃H₇)+MgCl₂

To a stirred solution of excess ^(i)PrMgCl in butyl diglyme (750 mL,1.05 moles) was added at room temperature neat Me₃GeCl (130 g, 0.848moles) in a controlled manner via 16 gauge stainless steel cannula. Theaddition took 3 hours during which time the temperature rose to ca. 50°C. After the addition was completed and the mixture was allowed to coolto room temperature, crude product was isolated by full vacuum transferwith heating of the pot gradually to 85° C., into a dry ice cooledreceiver. The crude product was atmospherically distilled using a 1.5 ftvacuum jacketed packed column to yield a main fraction distillingbetween 93-97° C. (105 g, Yield=77%). ¹H nmr spectrum contained adoublet at 1.0 ppm, a multiplet at 0.94 ppm, and a singlet at 0.06 ppmcorresponding to CH₃, CH and GeCH₃ respectively.

EXAMPLE 17

Dimethylaminopropyltrimethylgermane was synthesized according to thefollowing equation.(CH₃)₃GeCl+[{N(CH₃)₂}C₃H₆]MgCl→[{N(CH₃)₂}C₃H₆]Ge(CH₃)₃+MgCl₂

To a stirred solution of excess dimethylaminopropylmagnesium chloride intetrahydrofuran (0.38 moles) was added at room temperature neat Me₃GeCl(52 g, 0.34 moles) in a controlled manner. The addition took 1 hourduring which time the temperature rose to ca. 44° C. After the additionwas completed and the mixture was heated to 75° C. for 1 hour. Thereaction mixture was then allowed to cool to room temperature, andde-ionized water (150 mL) was added to the reaction mass in controlledmanner. The organic layer containing crude product was isolated bysiphoning. The aqueous layer was extracted with diethylether (100 mL),and the extracted solution was combined with the product. The organiclayers were dried over molecular sieves (5 Å) over 16 hours. Thesolvents (tetrahydrofuran and diethylether) were removed by atmosphericpressure distillation, while the crude product (45 g) was obtained byvacuum distillation. ¹H nmr spectrum confirmed the product to be thedesired dialkylaminopropyltrimethylgermanium.

EXAMPLE 18

Tertiary-butyl germanium trichloride was synthesized according to theequation:tBuMgCl+GeCl₄→tBuGeCl₃+MgCl₂

To a cool stirred solution of germanium tetrachloride (95 g, 0.443moles) in butyl diglyme (150 mL) maintained at 0° C., was added dropwisea solution of t-butyl magnesium chloride in butyl diglyme (0.422 moles,410 mL of 1.03 M) via pressure equalized addition funnel. A slightexcess of germanium tetrachloride was maintained. This addition lastedfor 120 minutes. When the addition was complete, the resulting mixturewas allowed to slowly warm to room temperature after which a suspensionof magnesium chloride was observed. The product, t-butyl germaniumtrichloride was isolated by vacuum distillation from the magnesiumchloride and butyl diglyme. The vacuum was slowly lowered to full vacuumand the temperature was raised to 50° C. to obtain the final product.The crude product was found to be contaminated with trace butyl diglymeas verified by FTNMR. The crude product was further purified by a secondvacuum distillation.

EXAMPLE 19

Tertiary-butyl germanium trichloride was synthesized according to theequation:tBuMgCl+GeCl₄→tBuGeCl₃+MgCl2

To a cool stirred solution of germanium tetrachloride (100 g, 0.443moles) in linear alkyl benzene (200 mL) maintained at 0° C., was addeddropwise a solution of t-butyl magnesium chloride in diethyl ether(0.466 moles, 233 mL of 2.0 M) via pressure equalized addition funnel. Aslight excess of germanium tetrachloride was maintained. This additionlasted for 120 minutes. When the addition was complete, the resultingmixture was allowed to slowly warm to room temperature after which asuspension of magnesium chloride was observed. The product, t-butylgermanium trichloride, and diethyl ether were removed from the reactionmixture by vacuum distillation. The resultant material was thensubjected to atmospheric distillation to remove the ether. After theremoval of ether, pure product was obtained by the purification of crudeproduct by vacuum sublimation (40 g, Yield=37%).

EXAMPLE 20

A group of Si_(x)Ge_(1-x) epitaxial structures are expected to be grownby MOCVD on (001) sapphire substrates. MOCVD is performed usingbis(dimethylamino)silane and bis(dimethylamino)-germane as precursors,and H₂ and/or N₂ as the carrier gases. For this group of layers, a 1 to2 μm thick Si_(0.9)Ge_(0.1) layer is first expected to be grown on asilicon substrate. Subsequent layers of composition Si_(0.8)Ge_(0.2),Si_(0.7)Ge_(0.3), and Si_(0.6)Ge_(0.4) are expected to be grown byincreasing the mass flow rate of the germanium precursor. The growthtemperature is maintained between 350° C. and 450° C. After depositionof the Si_(1-x)Ge_(x) graded layers, the silicon precursor flow iscontinued with the germanium precursor flow completely switched off, inorder to obtain abrupt interfaces. Silicon deposition is thus carriedout using the graded SiGe as the underlying layer, and epitaxialstrained silicon layer is expected to be deposited as the cap layer.

Germanium Precursors Silicon Precursors Di-tert-butyl germaneDi-tert-butyl silane Mono-tert-butyl germane Mono-tert-butyl silaneTri-tert-butyl germane Tri-tert-butyl silane Mono(dimethylamino) germaneMono(dimethylamino) silane Bis(dimethylamino) germane Bis(dimethylamino)silane Tris(dimethylamino) germane Tris(dimethylamino) silaneMono-tert-butyl germane Mono(dimethylamino) silaneTert-Butyl(dimethylamino) germane Di-tert-butyl silane Iso-Propylbis(dimethylamino) germane Bis(diethylamino) silane Di-tert-butylgermane Mono-tert-butyl silane Methyl tert-butyl germane Mono-tert-butylsilane Mono-iso-butyl germane Dichlorosilane Trichloro iso-butyl germaneDisilane Trichloro tert-butyl germane Tetrachlorosilane Trichloro ethylgermane Dimethyl dichlorosilane

1. A method of depositing a metal-containing film on a substratecomprising the steps of: a) conveying one or more organometalliccompounds of formula I in a gaseous phase to a deposition chambercontaining a substrate,

wherein M is Ge; R¹ and R² are independently chosen from H, alkyl,alkenyl, alkynyl and aryl; each R³ is independently chosen fromn-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl,cyclopentyl, hexyl, cyclohexyl, alkenyl, alkynyl and aryl, provided thatnone of R³ is cyclopentadienyl; each R⁴ is independently chosen from(C₃-C₁₂)alkyl; X is halogen; a=0-3; b=0-3; c=0-3; d=0-2; e=0-4; anda+b+c+d+e=4; wherein B³≠R⁴; wherein the sums of a+b and a+d are each ≦3;b) decomposing the one or more organometallic compounds in thedeposition chamber; and c) depositing a metal-containing film comprisinggermanium on the substrate.
 2. The method of claim 1 wherein d=1-2 ande=1-3.
 3. The method of claim 1 wherein R⁴ is branched or cyclic(C₃-C₁₂)alkyl.
 4. The method of claim 1 wherein the organometalliccompounds is chosen from iso-butylgermane and (NMe₂) GeCl₃.
 5. Themethod of claim 1 wherein c=1-3.
 6. A method of depositing agermanium-containing film on a substrate comprising the steps of: a)conveying one or more organometallic compounds of formula IIA or IIB:

wherein R¹ and R² are independently chosen from alkyl, alkenyl, alkynylor aryl; each R³ is independently chosen from (C₁-C₁₂)alkyl, alkenyl,alkynyl and aryl; each R⁴ is independently chosen from branched andcyclic (C₃-C₅)alkyl; each R⁵ is independently chosen from (C₁-C₁₂)alkyl,alkenyl, alkynyl and aryl; X is halogen; a′=0-3; b′=0-2; c′=1-3; d′=0-3;a′+b′+c′+d′=4; a″=0-2; b″=0-2; e″=1-2; f″=0-2; a″+b″+e″+f″=4; wherein atleast two of a″, b″and f″≠0; provided that R⁵≠CH₃ when a″=1, e″=1, f″=2,and R⁴=(CH₃)C; and provided that R³ is branched or cyclic (C₃-C₅)alkylwhen c′+d′=4, in a gaseous phase to a deposition chamber containing asubstrate; b) decomposing the organometallic compound in the depositionchamber; and c) depositing a germanium-containing film on the substrate.7. A method of depositing a metal-containing film comprising the stepsof: a) providing a substrate; b) disposing the substrate in a depositionchamber; c) conveying one or more organometallic compounds in a gaseousphase to the deposition chamber, wherein one organometallic compound isiso-butylgermane; and d) depositing a metal-containing film on thesubstrate, wherein the metal-containing film comprises germanium.
 8. Themethod of claim 7 wherein the organometallic compound comprises one ormore of silane and dichlorosilane.
 9. The method of claim 8 wherein themetal-containing film further comprises silicon.
 10. A method ofdepositing a multi-layer structure on a substrate comprising the stepsof: a) providing a substrate; b) disposing the substrate in a depositionchamber; c) conveying iso-butylgermane in a gaseous phase to thedeposition chamber; d) decomposing the iso-butylgermane to form agermanium-containing film on the substrate; e) conveying a siliconprecursor chosen from one or more of silane and dichlorosilane in agaseous phase to the deposition chamber; f) decomposing the siliconprecursor; and g) depositing a silicon-containing film substrate. 11.The method of claim 10 wherein the multi-layer structure comprisesSi_(1-x)Ge_(x), wherein x ranges from 0 to 0.50.